Many optogenetic applications involve injecting light into a living organism. Many experiments are done on laboratory mice worldwide to develop this promising field of health sciences. In this context, the mouse has an implant on its head to inject the light into their brain cells, and typically keeps this implant until the end of its life. The implant has one end of a fiber-optic patch cord (or cable), the other end of which is connected to a light source.
As the mouse moves about in its cage, it can subject the fiber-optic patch cord to torsion which is both uncomfortable for the mice and can subject the fiber-optic patch cord to torsion, which is undesired. To this end, it was known in the art to use two patch cord sections connected to one another via a rotary joint, which allowed the mouse to move more freely in the cage. However, this led to two optical connections in the patch cord, a first one between the light source and the first section, and a second one across the rotary joint, which affected the beam quality in a way which was unsatisfactory for at least some optogenetic applications. Henceforth, there remained room for improvement.